The present invention relates to photographic printers. In particular, the present invention relates to an improved system by which an operator of a photographic printer may provide corrections for negatives which would otherwise print incorrectly.
Printers produce color or black and white prints or transparencies from photographic film originals (generally negatives). High intensity light is passed through the film and imaged on the photosensitive print medium (film or paper). The photographic emulsion layers on the print paper or film are exposed and subsequently processed to produce a print of the scene contained in the original.
A critical portion of a photographic printer is the exposure control, which controls the exposure of the photosensitive medium in order to ensure that the image on the photosensitive medium is properly exposed. The exposure control may utilize inputs from several different sources in order to determine the proper exposure. Most automatic and semi-automatic printers use large area transmission density (LATD) sensors to sample the light transmitted by the negative either prior to or during the exposure. Control of the exposure is determined using a method known as "integration to grey". In addition, most photographic printers provide the means by which the operator may enter color and overall density corrections from an operator control panel. These corrections modify the exposure which would otherwise be provided in accordance with the LATD sensor signals.
The typical photographic printer provides the operator with a plurality of incremental correction keys by which the operator may request incremental changes in color or in overall density. By means of these correction buttons or keys, the operator may request increases or decreases in overall density from that provided by the integration to grey, or increases or decreases in a particular color (while maintaining overall density constant). A density button correction changes all three exposure times by a fixed percentage, while a color button correction changes the exposure times by reciprocal percentage amounts. Color/density button increments are ideally of constant density value throughout the buttoning range.
A skilled operator is able to identify negatives which will require button corrections. In many cases, these corrections will be only a single button, while in other cases, the required corrections may require more than one button.